Flashbang

noun
1. The sudden appearance of a large crowd of caucasian individuals, obscuring one's view of their surroundings, typically in a relatively small space, such as a train in a subway.

noun
2. a grenade that creates a flash and a high pitched noise intended to stun or disorient targets without actually injuring or seriously harming them.

1: "It took you a while to get home from the city. Did something happen on the way back?"
2: "Turns out the Taylor Swift concert had just ended the same time I intended to leave. I tried to get onto the train as early as I could, but all public transportation in the area was hit with a flashbang, could barely breathe in there!"